Process of making deterrent-coated and graphite-glazed smokeless powder

ABSTRACT

An improved process for manufacture of deterrent-coated and graphite-glazed smokeless powder is provided with deterrent coating and graphite glazing being done in an aqueous slurry at elevated temperatures.

United States Patent 1151 3,637,444

Bonyata et a1. [45] Jan. 25, 1972 54] PROCESS OF MAKING DETERRENT- 32333 172/195; Woodbridge 149 9 19 Wagner 149/10 2,113,418 4/1938Woodbridge ....149 10 SMOKELESS POWDER 2,152,509 3/1939 Troxler....149/10 [72] inventors: John 0. Bonyata, Mountain Lakes; Lynn11791312 11/1939 Allison Rohrbaugh Lake Hopatcong, both of 2,346,1254/1944 Goodyear. ....149/ 10 I N1 2,440,267 4/1948 Hale ..l49/l02,407,967 9/1946 Thomson.. ..149/9 [73] Assigneez Hercules Incorporated,Wilmington, Dei. 2 3 5 723 2 195 Cook 149 10 [22] Filed: AP 14, 19693,506,505 4/1970 Herzog et a1 ..149/9 [21] Appi. No; 816,023 PrimaryExaminer-Car! D. Quarforth Assistant Examiner-Stephen J. Lechert, Jr.[521 11.5.0 ..149/10,149/9, 149/11, Gramswwa" 51 1111.01. ..C06b 19/02[57] ABSTRACT [58] Field of Search 14 /100, 7, ll, An improved processfor manufacture of deterrent-coated 1 /1 264/3 and graphite-glazedsmokeless powder is provided with deterrent coating and graphite glazingbeing done in an aqueous [56] References Cited slurry at elevatedtemperatures.

UNITED STATES PATENTS 20 Claims, No Drawings 1,393,623 1 0 1 921 Henning149/9 PROCESS OF MAKING DETERRENT-COATED AND GRAPHITE-GLAZED SMOKELESSPOWDER This invention relates to a process for manufacture of smokelesspowder in which each of the processing steps of nitrocellulosedensification, deterrent coating, and graphite glazing can be performedin an aqueous slurry. More particularly this invention relates to anaqueous slurry process for rapidly deterrent coating and graphiteglazing of granulated nitrocellulose particles. In still another aspect,this invention relates to an aqueous slurry process for manufacture ofdeterrent-coated and graphite-glazed double-base smokeless powder from asingle-base type of granulated nitrocellulose in which all of theprocessing steps are conducted in an aqueous slurry.

The conventional process for manufacture of smokeless powder involves asa first step the granulation of nitrocellulose. In this processwater-wet nitrocellulose is dehydrated with denatured alcohol in ablocking press. The resulting dehydrated nitrocellulose is broken up inthe blocking press and subsequently masticated in a large mixer by theaddition of solvents such as denatured ethyl alcohol and acetone to forma homogeneous stiff dough. Energetic plasticizers such as nitroglycerinare admixed with the dough if a double-base composition comprised ofnitroglycerin and nitrocellulose is to be made. The stiff dough isblocked in large hydraulic presses and subsequently extruded at highpressure into strands of powder. The strands of powder are cut into adesired length. These particles are then dried for several days toremove processing solvents and water. The particles of powder producedare referred to herein as smokeless powder. Some of these driedparticles can be coated with various buming rate deterrents if desiredin order to obtain progressive burning smokeless powder. The coatedsmokeless powder particles or granules are dried and then glazed withgraphite to prevent the build up of a static charge on the granules andto increase ease of handling.

The foregoing process is tedious, requires considerable amounts ofmassive and expensive equipment and requires much skilled labor in orderto produce a quality product. Over the years numerous attempts have beenmade to develop processes to obviate one or more of the processingdifficulties encountered in this process for manufacture of smokelesspowder. Many of these processes, sometimes referred to as nitrocellulosedensification processes, are directed to alternative methods forgranulation of nitrocellulose which eliminate long mixing times,extrusion of doughs, and cutting of strands of powder. One such processis the Ball Powder Process and is disclosed in U.S. Pat. No. 2,027,114.A modification of this process is disclosed in U.S. Pat. No. 2,885,736.

Other processes have been developed for granulation of nitrocellulose inwhich water wet nitrocellulose is agitated in a slurry to which solventsfor the nitrocellulose are added to partially gelatinize thenitrocellulose without dissolution thereof. The solvent is then removedfrom the slurry producing smooth, hardened, densified nitrocelluloseparticles. Such processes are described in U.S. Pat. Nos. 2,946,673 and2,948,601. A recent patent disclosing both a granulation method forfibrous nitrocellulose by a nitrocellulose densification process and aprocess for manufacture of double base smokeless powder therefrom isU.S. Pat. No. 3,346,675 to J. Sapiego. With the exception of theconventional process all of the foregoing processes have one basic stepin common, i.e., that nitrocellulose is granulated through the action onnitrocellulose of one or more solvents for nitrocellulose dispersed inthe presence of a nonsolvent for nitrocellulose, such as water.

The product produced from the foregoing granulation processes which areintended to represent the basic prior art process is particles ofgranulated nitrocellulose. These particles can be deterrent coated,graphite glazed, and converted from single-base particles to double-baseparticles, (where applicable) with each step performed in an aqueousslurry in accordance with the process of this invention. The process ofthis invention is particularly suitable for manufacture of smokelesspowder from granulated nitrocellulose prepared by a process such as isdescribed in U.S. Pat. No. 3,346,675, so that each step of the processincluding granulation is performed in an aqueous slurry. However,granulated nitrocellulose in particle form manufactured by theconventional solvent process can be employed. The process of thisinvention provides a highly safe method for deterrent coating, graphiteglazing, and nitroglycerin absorption of granulated nitrocelluloseparticles since the granulated nitrocellulose is processed in an aqueousslurry in each step.

Broadly, the process of this invention comprises (a) forming a slurry ofgranulated nitrocellulose particles and water, (b) admixing in theslurry of step (a) a burning rate deterrent or finely divided graphiteto form a slurry comprising a continuous phase of water and a dispersedphase of burning rate deterrent or finely divided graphite, (c) heatingthe slurry to a temperature at which the burning rate deterrent, whenpresent, melts but to at least 150 F. until substantially all of theburning rate deterrent or finely divided graphite adheres to thegranulated nitrocellulose particles, and (d) separating smokeless powderfrom the slurry.

In the deterrent-coating and graphite-glazing steps heretoforedescribed, it has been found that if energetic plasticizers are employedin manufacture of the granulated nitrocellulose particles some of theseplasticizers are extracted out of the particles into the water phase ofthe slurry causing a change in the composition of the resulting coatedand glazed smokeless powder. In the process of this inventiontemperatures of at least 150 F. are required in order to achieve rapidand suitable deterrent coating and glazing. At these temperaturesplasticizer extraction rates increase. While powder can be manufacturedwith an amount of excess plasticizer equivalent to that which would beextracted under a particular set of processing conditions for aqueousslurry deterrent coating and graphite glazing, it is in generalundesirable from an economic and process standpoint to do so. Toeliminate loss of explosive plasticizer from a powder composition wherecomposition is critical as is often times required, it is necessary toemploy in the water in the aqueous slurry an equilibrium concentrationof plasticizer. This equilibrium concentration of plasticizer isdependent upon the slurry composition, and the slurry temperature; theequilibrium concentration of nitroglycerin as an energetic plasticizerbeing preferably from about 0.1 to about 0.3 percent by weight based onthe weight of the water in the aqueous slurry. The term equilibriumconcentration" is used herein with reference to energetic plasticizer isdefined as a concentration of energetic plasticizer in the aqueousslurry at which there is substantially no tendency for the plasticizerto be either absorbed into or extracted from the granulatednitrocellulose particles during the processing cycle. If the granulatednitrocellulose contains no plasticizers, then no extraction problemexists.

In the aqueous slurry process of this invention it may be desired tomanufacture a double-base-type smokeless powder from granulatednitrocellulose of the single-base type. In this case, prior to additionof deterrent to the slurry of granulated nitrocellulose and water, anenergetic plasticizer is slowly admixed in the slurry at ambienttemperature in an amount of from about 5 to about 40 percent by weight,based on the weight of the granulated nitrocellulose. The slurry is thenheated to a temperature of from about F. to about F. and is maintainedin this temperature range for from onehalf hour to about 4 hours. Duringthis period the energetic plasticizer completely penetrates thegranulated nitrocellulose. The quantity of energetic plasticizer thatremains in the water phase of the slurry after complete penetration ofthe plasticizer into the granulated nitrocellulose is the equilibriumconcentration of plasticizer. The deterrent coating and graphite glazingsteps heretofore described are then performed. The deterrent-coated andgraphite-glazed smokeless powder is separated from the aqueous slurry byany suitable means such as decantation or centrifugation and dried.

The following examples will more fully illustrate the aqueous slurryprocess of this invention. All parts and percentages are by weightunless otherwise specified.

Example 1 illustrates granulation of fibrous nitrocellulose in anaqueous slurry to produce granulated nitrocellulose of the single basetype.

EXAMPLE 1 A slurry is prepared in a vessel by admixing 72.5 parts ofwater and 8.08 parts of fibrous nitrocellulose in the vessel andagitating the admixture with a Cowels high shear agitator having a12-inch diameter blade operating at 900 r.p.m. To this admixture isadded 0.074 part of diphenyl amine and 0.098 part of barium nitrate. Theslurry is heated from ambient temperature (68 F.) to 130 F. To thewarmed slurry is added 19.42 parts of methyl isobutyl ketone over aperiod of 19 minutes. About 0.074 part of methyl cellulose is added tothe warmed slurry after about one-fourth of the total methyl isobutylketone has been added. After all the MIBK is added, the temperature ofthe slurry is progressively increased to remove methyl-isobutyl ketoneas a water azeotrope. Agitation is maintained during solvent removal butis reduced to 500 r.p.m. after the temperature of the slurry has reached180 F. and been held at that temperature for 75 minutes. Followingremoval of the solvent, the slurry is cooled to at least 125 F. andcentrifuged at 1,400 r.p.m. in a 12-inch diameter basket centrifuge toremove the major portion of the process water. Water-wet densifiednitrocellulose particles are recovered having a particle sizedistribution as set forth in table 1.

The following example illustrates nitroglycerin absorption by granulatednitrocellulose in an aqueous slurry to provide double base typesmokeless powder.

EXAMPLE 2 Nitroglycerin Absorption About 8.33 parts of granulatednitrocellulose particles prepared in example 1 are admixed in 100 partsof water at ambient temperature. This admixture is agitated mildly witha propeller agitator to fonn a slurry comprised of a continuous aqueousphase of water and a dispersed phase of densified nitrocellulose. Tothis slurry is added 2.36 parts of nitroglycerin. The nitroglycerin isdispersed in the slurry and at no time is this dispersion ofnitroglycerin in water or the dispersed granulated nitrocelluloseparticles allowed to settle. Following addition of the nitroglycerin tothe slurry, the slurry temperature is rapidly increased to 115 F. andheld at that temperature for about 2 hours. During this heating periodthe nitroglycerin completely penetrates the densified nitrocellulose.The resulting slurry is dewatered in a 12-inch diameter basketcentrifuge operating at 1,000 r.p.m. The nitroglycerin content of thewater is measured and is about 0.2 percent by weight based on the weightof the water. This represents the equilibrium concentration ofnitroglycerin in this slurry. Substantially all nitroglycerin admixed inthe slurry is absorbed by and penetrates the granulated nitrocellulose.

The following example illustrates deterrent coating of double base typesmokeless powder in an aqueous slurry.

EXAMPLE 3 Deterrent Coating About 10.7 parts (dry bases) of thedouble-base smokeless powder prepared in example 2 is admixed with 131parts of water at 68 F. The admixture is mildly agitated in a vesselequipped with a propeller-type agitator. To the resulting slurry isadded 0.562 parts of symmetrical diethyl-diphenyl urea (ethylcentralite) in flake powder form corresponding to (MIL-E-ZSS-class 2).The slurry is heated to 175 F. and maintained at this temperature forabout 15 minutes. This temperature is slightly above the melting pointof the ethyl centralite. Substantially quantitative deposition of theethyl centralite on the surface of the smokeless powder is achievedduring this heating period. The temperature of the slurry is thenreduced to 120 F. following the deterrent coating of the granulatednitrocellulose and the slurry is centrifuged. Water wet deterrent coatedsmokeless powder is recovered containing about 30 weight percent waterbased on the weight of the water wet powder. The total deterrent-coatingoperation is completed in less than minutes. The deterrent-coatedparticles are dried. There is substantially no particle agglomeration inthe dried deterrent-coated powder.

The following example illustrates graphite glazing in an aqueous slurryof smokeless powder particles in which granulation, nitroglycerinabsorption and deterrent coating are each conducted in an aqueousslurry.

EXAMPLE 4 Smokeless powder is prepared by granulating fibrousnitrocellulose (13.25 percent N) following the procedure of example 1.The granulated nitrocellulose particles are admixed in an aqueous slurryof nitroglycerin following the procedure of example 2 and absorb 16percent nitroglycerin from the slurry. The resulting double-basegranulated nitrocellulose is centrifuged. The wet particles arereslurried in water so that 13.4 parts granulated double-basenitrocellulose particles are dispersed in about 125 parts of water. Theslurry is agitated at about 70 F. and 0.53 parts ethyl centralite areadmixed therewith. Agitation is maintained to keep the granulatednitrocellulose and ethyl centralite dispersed in the slurry. The aqueousslurry is heated to about 175 F. After 5 minutes of heating at thistemperature 0.25 part of colloidal graphite (type GPW, an aqueous pastecontaining 22 percent by weight solids and sold by Graphite ProductsCorporation) is added to the slurry. Agitation of the slurry and heatingat about 175 F. are continued for an additional 10 minutes.Substantially quantitative deposition of colloidal graphite on theparticles is achieved. The resulting slurry of deterrent coated andgraphite glazed smokeless powder is cooled to F., centrifuged and dried.

The following example illustrates incomplete nitroglycerin absorptionfrom an aqueous slurry by a singlebase type granulated nitrocellulosemanufactured by a solvent densification process.

EXAMPLE 5 About 10.3 parts of nitrocellulose (13.2 percent N) isslurried in gt.68 parts of water. The slurry is subjected to high shearagitation with a Cowels high shear agitator having a 12- inch diameterblade operating at 800 r.p.m. To this admixture is added 0.09 partdiphenylamine, 0.113 part barium nitrate, and 0.1 13 part of triphenylphosphate. The slurry is heated to F. and 21.6 parts of methyl isobutylketone is added to the slurry over a 20-minute period. About 0.09 partof methyl cellulose is added to the slurry after addition of one-fourthof the methyl isobutyl ketone. The methyl isobutyl ketone is removedfrom the slurry as a water azeotrope. The resulting water-wet granulatednitrocellulose is centrifuged. The waterwet granulated nitrocellulose isreslurried in water to form a slurry comprised of 10.7 parts granulatednitrocellulose and 124 parts water. While the slurry is vigorouslyagitated 1.8 parts of nitroglycerin is added to the slurry. Thetemperature of the slurry is increased from ambient temperature to 80 F.and held at this temperature for 15 minutes. The resulting mixture iscentrifuged at low r.p.m. The water from the centrifuge is sent to adecanter and unabsorbed nitroglycerin recovered. About 55 percent of thenitroglycerin added to the slurry is absorbed by the granulatednitrocellulose. The granulated nitrocellulose recovered has a particlesize distribution as set forth in table I.

The following example illustrates complete absorption of nitroglycerinfrom an aqueous slurry by a single-base type granulated nitrocelluloseprepared by a solvent densification process.

EXAMPLE 6 About 8.33 parts of granulated nitrocellulose is preparedfollowing the general procedure as set forth in example 1 with somevariations in processing conditions. The resultant granulatednitrocellulose has a particle size distribution and bulk density as setforth in table I. The resulting granulated nitrocellulose, about 8.33parts, is slurried in 100 parts of water. About 2.36 parts ofnitroglycerin is added to the slurry. The slurry is heated to 80 F. andmaintained at that temperature for about 15 minutes. After 15 minutes ofheating the aqueous slurry becomes substantially clear indicatingcomplete absorption of the nitroglycerin by the granulatednitrocellulose. The slurry is divided into two portions. The water iscarefully drained from one portion of the granulated nitrocelluloseparticles. Only an equilibrium concentration of nitroglycerin is in thedecanted water. The second portion of the slurry is mildly centrifuged.The resultant water is very cloudy indicating removal of nitroglycerinfrom the surface of the granulated nitrocellulose particles.

TABLE I Particle Size Distribution Granulated Nitrocellulose Thefollowing example illustrates graphite glazing and deterrent coating ofsmokeless powder in which the granulated nitrocellulose is made by theconventional solvent process.

EXAMPLE 7 Granulated nitrocellulose in the form of base grain andmanufactured by the solvent process in which it is extruded through a0.065-inch O.D. X 0.0l5-inch [.D. die and curs at 300 cuts per linealinch is dried and is slurried in water at ambient temperature (65 F.).About 12.6 parts of the granulated nitrocellulose is combined with 153parts of water. About 0.65 part of Vinsol resin, fully definedhereinafter, is dispersed in the slurry. The slurry which is comprisedof a dispersed phase of granulated nitrocellulose and finely powderedVinsol and continuous phase of water is heated above the melting pointof the Vinsol and held at 190 F. for 15 minutes. After this heatingcycle the slurry is cooled, filtered and dried in a conventional dryhouse. The resulting deterrent coated powder is blended with base grainof the same powder composition. Ballistic results for the powder blendare set forth in table II below. Comparison is made with aconventionally deterred powder of the same powder composition.

EXAMPLE 8 Example 7 is repeated with the exception that the cutgranulated nitrocellulose (base grain) is not dried but is slurried inwater while still water wet and containing about 10 percent by weight ofprocessing solvent based on the weight of dry base grain. About 12.6parts of the powder (dry basis) are dispersed in 153 parts of water, and0.65 part of finely powdered Vinsol resin is dispersed in the slurry.The slurry is heated to 190 F. and maintained at that temperature forminutes. The Vinsol resin melts and is deposited on the surface of thegranulated nitrocellulose. During this heating period processingsolvents in the granulated nitrocellulose are extracted into the waterphase of the slurry. The powder is separated from the slurry dried andblended with nondeterred granulated nitrocellulose (base grain) andballistically tested. Results are set forth in table ll below.

TABLE II [Ballistics aqueous slurry deterred powder] Standard Aqueousslurry deterrent deterrent coating coating Powder process (control) Ex.7 Ex. 8

Percent Vinsol on base grain 6. 0 5. 0 5. 0 Blend ratio, deterred/basegrain 70/30 40/60 40/60 Coating tlme at 190 F. (minutes) 30 15 15Stability; German test (minutes) 35 50 45 Charge weight in shell, grains20 20 20 Ballistics:

Velocity, feet/second 1, 206 l, 294 1, 139 Pressure, p.s.i 9, 820 9, 6009,100

Ballistics on Federal 12 gauge shell 1% ounee#7} shot.

As can be seen from table II the powder blends employing the aqueousslurry deterrent coated powder, examples 7 and 8, require less of thedeterrent-coated powder in the blend in order to achieve ballisticssubstantially the same as a powder blend employing standarddeterrent-coated powder. A more uniform coating of powder by thedeterrent in the aqueous process of this invention is attributed to thisresult. Higher German stability values are also obtained with powderobtained by blending deterrent coated powder manufactured by the aqueousslurry process of this invention probably due to increased coatinguniformity of the deterrent coated powder.

In the aqueous slurry process heretofore described granulatednitrocellulose to be deterrent coated is slurried in water in an amountto preferably provide a slurry containing from about 8 to about 20percent granulated nitrocellulose. The slurry is agitated sufficientlyto fully disperse the granulated nitrocellulose throughout the waterphase of the slurry. The deterrent-coating agent is then admixed withthe slurry at a temperature below the melting point of the coatingagent. The deterrent-coating agents are employed in powdered or finelydivided form and are admixed into the slurry at a temperature belowtheir melting point. The slurry is then heated to a temperature slightlyabove the melting point of the deterrent but to at least 150 F. Theslurry is held at a temperature slightly above the melting point of thedeterrent until substantially all the deterrent adheres to the surfaceof the granulated nitrocellulose, which generally requires about 15minutes.

Suitable deterrent-coating materials which can be employed includematerials which will penetrate the smokeless base grain on prolongedheating such as symmetrical diethyl diphenyl urea (ethyl centralite),symmetrical dimethyl diphenyl urea, solid dinitrotoluene, triphenylphosphate, and the like.

Other deterrent coatings which can be employed which do not penetrateinto the smokeless base grain particle but which are absorbed on to thesurface of the particle include Vinsol resin, a dark thermoplastic resinhaving an acid number of about a softening point of about C.; insolublein hydrocarbon solvent; soluble in polar solvents, and availablecommercially under the trademark Vinsol from Hercules lncorporated. Thisresin is preferably employed in pulverized form. Still other deterrentcoating materials which can be employed include glyceryll2-hydroxy'stearate having an acid number of 2, an iodine value (WIJS)of 29, and a hydroxyl number of about 158; and glycerylmonohydrostearate having an acid number of 3, and iodine value (WUS) of5, and a hydroxyl number of 320. These materials are availablecommercially as Castorwax MP-80 and Paracin 13 respectively.

Mixtures of two or more of any of the deterrent coating materials can beemployed if desired.

The amount of deterrent coating material which is admixed and dispersedin the aqueous slurry deterrent coating step in the process of thisinvention will vary depending on the ballistic result desired from aparticular powder. In general the amount of deterrent will vary fromabout 3 lzto about 8 percent by weight, based on the weight of thegranulated nitrocellulose. The smokeless powder resulting from deterrentcoating of granulated nitrocellulose is referred to as progressivebuming smokeless powder.

Graphite glazing of granulated nitrocellulose is accomplished in thesame vessel in which deterrent coating is performed. In the glazing stepof this process colloidal graphite, granulated nitrocellulose (eitherdeterred or nondeterred) and water are slurried. The slurry is agitatedso that it is comprised of a dispersed phase of colloidal graphite anddensified nitrocellulose particles and a continuous phase comprised ofwater. The slurry is heated to a temperature of at least 150 F. andheating and agitation of the slurry is maintained until substantiallyall of the graphite has adhered to the surface of the smokeless powder.

A preferable procedure of graphite glazing is readily accomplished bysimply admixing the graphite in the aqueous slurry during the deterrentcoating step. The graphite is preferably added after a substantialamount of deterrent has adhered to the surface of the smokeless powder.This occurs after about the first 5 minutes of heating at a temperatureof 150 F. or above. The granulated nitrocellulose to be glazed isslurried in water in an amount to provide a slurry containing from about8 to about 20 percent densified nitrocellulose. The slurry temperaturemust be at least 150 F. to obtain a rapid glazing rate. Time requiredfor completion of graphite glazing will vary depending on thetemperature of the slurry, glazing rate being faster at higher slurrytemperatures. Time required to achieve essentially quantitativedeposition of graphite on the granulated nitrocellulose at a slurrytemperature of 175 F. is about 10 minutes.

The amount of graphite applied to either deterred or nondeterredsmokeless powder is from about 0.1 to about 2.0 percent by weight basedon the weight of the granulated nitrocellulose.

In the process of this invention double-base powder can be readilymanufactured from granulated nitrocellulose by adding energeticplasticizer to the aqueous slurry of granulated nitrocellulose andwater. Nonenergetic plasticizers can be admixed with the energeticplasticizer if desired. The energetic plasticizer is added to the slurryat any rate permissible with respect to safety. Agitation of the slurrymust be maintained at a level sufficient to keep the plasticizer andgranulated nitrocellulose particles fully dispersed in the water phaseof the slurry at all times in order to obtain uniform absorption of theplasticizer by the granulated nitrocellulose. Mild agitation with apropeller or paddle-type agitator is sufficient. The slurry to which theenergetic plasticizer is admixed will contain from about 8 to aboutpercent by weight of granulated nitrocellulose and from about 80 toabout 92 percent by weight of water.

Time and temperature are important factors in obtaining completepenetration of energetic plasticizers into the granulated nitrocelluloseparticles. The term complete penetration" as used herein is defined tomean that the energetic plasticizer is not displaced or removed from thedensified nitrocellulose following absorption from an aqueous slurrywhen subjected to vigorous forces such as in centrifugation. This termis contrasted with complete absorption of energetic plasticizer which isdefined herein to mean that densified nitrocellulose has absorbed allthe energetic plasticizer from the slurry on to its surface, but whensubjected to vigorous forces such as centrifugation, a substantialamount of the energetic plasticizer can be removed from the surface ofthe densified nitrocellulose into the water phase of the slurry. Example1 illustrates a set of process conditions at which complete penetrationof nitroglycerin into the nitrocellulose particles occurs since only anequilibrium concentration of nitroglycerin can be detected in the waterresulting from centrifugation of the slurry. It is preferred andcritical to processing of large amounts of smokeless powder havingspecified compositions to have complete penetration of thenitrocellulose by the plasticizer. While absorption of energeticplasticizer by the nitrocellulose will take place in the aqueous slurryat ambient temperature, the rate of absorption is too slow to bepractical. Absorption temperatures of from about to about F. for fromabout one-half hour for the lowest concentration of energeticplasticizer to about 4 hours for the highest concentration of energeticplasticizer will result in complete penetration of the nitrocelluloseparticles by the plasticizer in accordance with this invention.

Energetic plasticizers which can be absorbed on densified nitrocelluloseinclude nitroglycerin, the nitrate esters of polyhydric alcoholsincluding diethylene glycol dinitrate, ethylene glycol dinitrate,triethylene glycol dinitrate, and the like. Nonexplosive plasticizerscan also be employed separately or in admixture with the explosiveplasticizers for nitrocellulose. Illustrative of nonexplosiveplasticizers which can be employed are triacetin, dibutyl phthalate,tricresyl phosphate, and the like.

The term granulated nitrocellulose as used herein is meant to encompassall types of colloided nitrocellulose particles, the nitrocellulose inall events being characterized by a nitrogen content of at least about11.3 weight percent, generally in the range of from about l2-13.5percent, and being in colloided form. As is well known, the single-baseparticles contain colloided nitrocellulose as the chief component, onthe order of from about 85 to 99 weight percent and the double-baseparticles contain the same colloided nitrocellulose component buttogether with an energetic plasticizer, usually nitroglycerin, or anequivalent energetic liquid nitric ester. Double-base particles containgenerally at least one-half colloided nitrocellulose and substantiallythe remainder nitroglycerin with other supplemental ingredients.Granulated nitrocellulose particles of the triple-base type containnitroguanidine in addition to colloided nitrocellulose, andnitroglycerin in proportions generally at least about 40 to 50 percentnitroguanidine and substantially the remainder colloided nitrocelluloseand nitroglycerin, the latter two being in any suitable relativeproportions, for example 1:1 to 4:1 of nitrocellulose to nitroglycerin.

Minor amounts of supplemental ingredients are utilized in theseparticles, particularly stabilizing agents, gelation agents, and thelike, all of which are well known in the art.

What we claim and desire to protect by Letters Patent is:

1. In the process of manufacture of burning rate deterrentcoated orgraphite-glazed smokeless powder from at least granulated nitrocellulosethe improvement comprising:

a. forming a slurry of at least granulated nitrocellulose particles andwater,

b. admixing in the slurry of step (a) a burning rate deterrent or finelydivided graphite to form a slurry comprising a continuous phasecomprising water, and a dispersed phase comprising burning ratedeterrent or finely divided graphite and granulated nitrocellulose,

c. heating the slurry to a temperature at which the burning ratedeterrent, when present, melts but to at least F. until substantiallyall of the burning rate deterrent or finely divided graphite adheres tothe granulated nitrocellulose particles, and

d. separating burning rate deterrent-coated or graphiteglazed smokelesspowder from the slurry.

2. The process of claim 1 wherein the slurry of step (a) is comprised offrom about 8 to about 20 percent by weight of granulated nitrocelluloseand from about 92 to about 80 percent by weight of water.

3. The process of claim 2 wherein the granulated nitrocellulose isdouble-base smokeless powder particles.

4. The process of claim 2 wherein the granulated nitrocellulose isdensified nitrocellulose particles.

5. The process of claim 3 wherein the water in the slurry has dissolvedtherein in equilibrium concentration of energetic plasticizer, saidenergetic plasticizer being of the same composition as the energeticplasticizer in the double-base smokeless powder.

6. The process of claim 5 wherein the energetic plasticizer isnitroglycerin.

7. The process of claim 6 wherein the water contains from about 0.1 toabout 0.3 percent by weight of nitroglycerin based on the weight of thewater.

8. The process of claim 2 wherein a burning rate deterrent is admixed inthe slurry of step (b) in an amount of from about 3% to about 8 percentby weight, based on the weight of the granulated nitrocellulose.

9. The process of claim 8 wherein the burning rate deterrent issymmetrical diethyl diphenyl urea.

10. The process of claim 9 wherein the slurry of step (c) is heated to atemperature of about 175 F.

11. The process of claim 8 wherein the burning rate deterrent is ahydrocarbon insoluble, dark thermoplastic resin which is soluble inpolar solvents and having an acid number of about 95 and a dropsoftening point of about 120 C.

12. The process of claim 11 wherein the slurry of step (c) is heated toa temperature of about 190 F 13. In the process of manufacture ofburning rate deterrentcoated and graphite-glazed smokeless powder fromat least granulated nitrocellulose, the improvement comprising:

a. fonning a slurry of at least granulated nitrocellulose particles andwater,

b. admixing in a burning rate deterrent to the slurry of step (a)forming a continuous phase comprising water and a dispersed phasecomprising granulated nitrocellulose particles and burning ratedeterrent,

c. heating the slurry to a temperature at which the burning ratedeterrent melts but to at least 150 F.,

d. admixing finely divided graphite to the heated slurry of step (c)said graphite being dispersed throughout the slurry and maintaining aslurry temperature of at least 150 F. until substantially all theburning rate deterrent and finely divided graphite have adhered to thegranulated nitrocellulose, and

e. separating burning rate deterrent-coated and graphiteglazed smokelesspowder from the slurry.

14. The process of claim 13 in which the finely divided graphite isadmixed in the slurry in an amount of from about 0.1 to about 2 percentby weight based on the weight of the granulated nitrocellulose.

15. The process of claim 13 wherein the burning rate deterrent issymmetrical diethyl diphenyl urea.

16. The process of claim 13 wherein nitroglycerin is admixed in theslurry of step (a) in an amount of from about 5 to about 40 percent byweight based on the weight of the granulated nitrocellulose forming aslurry comprising a continuous phase comprising water and a dispersedphase comprising granulated nitrocellulose and nitroglycerin andadmixing this slurry until substantially all the nitroglycerin but anequilibrium concentration of nitroglycerin in water has been absorbed bythe granulated nitrocellulose.

17. The process of claim 16 in which the slurry of water, granulatednitrocellulose, and nitroglycerin is heated to a temperature of fromabout F. to about F. for from about 30 to about 240 minutes to permitcomplete penetration of the nitroglycerin into the granulatednitrocellulose.

18. The process of claim 4 wherein nitroglycerin is admixed in theslurry of step (a) in an amount of from about 5 to about 40 percent byweight based on the weight of the densified nitrocellulose particlesforming a slurry comprising a continuous phase of water and a dispersedphase of densified nitrocellulose particles and nitroglycerin andadmixing this slurry until substantially all the nitroglycerin, but anequilibrium concentration of nitroglycerin in water, has been absorbedby the densified nitrocellulose particles.

19. The process of claim 19 in which the slurry of water,

densified nitrocellulose particles and nitrogl cerin is heated to atemperature of from about 100 to abou 140 F. for from about 30 minutesto about 250 minutes to permit complete penetration of the nitroglycerininto the densified nitrocellulose particles.

20. In a process for the manufacture of a smokeless powder selected fromthe group consisting of burning rate deterrentcoated, graphite-glazed,and buming-rate-deterrent-coated and graphite-glazed smokeless powders,from at least granulated nitrocellulose, the improvement comprising:

a. forming a slurry of at least granulated nitrocellulose particles andwater,

b. admixing in the slurry of step (a) at least one member selected fromthe group consisting of a burning rate deterrent and finely dividedgraphite, to form a resulting slurry comprising a continuous phasecomprising water and a dispersed phase comprising granulatednitrocellulose and each member of said group of burning rate deterrentand finely divided graphite admixed with the slurry of step (a) asdescribed,

c. heating the resulting slurry of step (b) at a temperature at whichthe burning rate deterrent, when present, melts but at at least F. untilsubstantially all of each member of said group of burning rate deterrentand finely divided graphite dispersed therein adheres to the granulatednitrocellulose particles, and

. separating from the slurry of step (c), as product of the process, asmokeless powder selected from said group of burning ratedeterrent-coated, graphite-glazed, and buming rate deterrent-coated andgraphite-glazed smokeless powders.

mg UNTTED STATES PATENT OFFICE CEHHCA'E @EF I EQ'TWN Patent No.3,637,444 Dated January 25, 1972 InVentO1(S) Bonyata and Rohrbauqh Case2 It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

- "T Q01. 5, Line 49 of p.p.

"curs" should be "cut" Col. 6, Line 20 (approx.) of p.p.

"1294 should be 1194" Col. 9, Line 22 of p.p.;

"95" should be "95" Col. 10, Line 21 of p.p.;

"Claim 19" should be "Claim 18" Signed and sealed this 3rd day ofOctober- 1972.

(SEAL) Attest:

EDWARD P LFLETCHERJR, ROBERT GUT'ISCHALK Attesting Officer Commissionerof Patents @2 3 UNTTED STATES PATENT OFFICE CERTIFICATE Gd CORRECTWNPatent No. 3,637,444 Dated n ry 25, 1972 Inventor(s) Bonyata andRohrbauqh Case 2 It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 5, Line 49 of p.p.

"curs" should be "cut" Col. 6, Line 20 (approx.) of p.p.;

"1294" should be "1194" Col. 9, Line 22 of p.p.;

"95" should be 95" Col. 10, Line 21 of p.p.;

fClaim l9 should be "Claim 18" Signed and sealed this 3rd day of October1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GUTTSCHALK Attesting Officer Commissionerof Patents

2. The process of claim 1 wherein the slurry of step (a) is comprised offrom about 8 to about 20 percent by weight of granulated nitrocelluloseand from about 92 to about 80 percent by weight of water.
 3. The processof claim 2 wherein the granulated nitrocellulose is double-basesmokeless powder particles.
 4. The process of claim 2 wherein thegranulated nitrocellulose is densified nitrocellulose particles.
 5. Theprocess of claim 3 wherein the water in the slurry has dissolved thereinin equilibrium concentration of energetic plasticizer, said energeticplasticizer being of the same composition as the energetic plasticizerin the double-base smokeless powder.
 6. The process of claim 5 whereinthe energetic plasticizer is nitroglycerin.
 7. The process of claim 6wherein the water contains from about 0.1 to about 0.3 percent by weightof nitroglycerin based on the weight of the water.
 8. The process ofclaim 2 wherein a burning rate deterrent is admixed in the slurry ofstep (b) in an amount of from about 3 1/2 to about 8 percent by weight,based on the weight of the granulated nitrocellulose.
 9. The process ofclaim 8 wherein the burning rate deterrent is symmetrical diethyldiphenyl urea.
 10. The process of claim 9 wherein the slurry of step (c)is heated to a temperature of about 175* F.
 11. The process of claim 8wherein the burning rate deterrent is a hydrocarbon insoluble, darkthermoplastic resin which is soluble in polar solvents and having anacid number of about 95* and a drop softening point of about 120* C. 12.The process of claim 11 wherein the slurry of step (c) is heated to atemperature of about 190* F.
 13. In the process of manufacture ofburning-rate-deterrent-coated and graphite-glazed smokeless powder fromat least granulated nitrocellulose, the improvement comprising: a.forming a slurry of at least granulated nitrocellulose particles andwater, b. admixing in a burning rate deterrent to the slurry of step (a)forming a continuous phase comprising water and a dispersed phasecomprising granulated nitrocellulose particles and burning ratedeterrent, c. heating the slurry to a temperature at which the burningrate deterrent melts but to at least 150* F., d. admixing finely dividedgraphite to the heated slurry of step (c) said graphite being dispersedthroughout the slurry and maintaining a slurrY temperature of at least150* F. until substantially all the burning rate deterrent and finelydivided graphite have adhered to the granulated nitrocellulose, and e.separating burning-rate-deterrent-coated and graphite-glazed smokelesspowder from the slurry.
 14. The process of claim 13 in which the finelydivided graphite is admixed in the slurry in an amount of from about 0.1to about 2 percent by weight based on the weight of the granulatednitrocellulose.
 15. The process of claim 13 wherein the burning ratedeterrent is symmetrical diethyl diphenyl urea.
 16. The process of claim13 wherein nitroglycerin is admixed in the slurry of step (a) in anamount of from about 5 to about 40 percent by weight based on the weightof the granulated nitrocellulose forming a slurry comprising acontinuous phase comprising water and a dispersed phase comprisinggranulated nitrocellulose and nitroglycerin and admixing this slurryuntil substantially all the nitroglycerin but an equilibriumconcentration of nitroglycerin in water has been absorbed by thegranulated nitrocellulose.
 17. The process of claim 16 in which theslurry of water, granulated nitrocellulose, and nitroglycerin is heatedto a temperature of from about 100* F. to about 140* F. for from about30 to about 240 minutes to permit complete penetration of thenitroglycerin into the granulated nitrocellulose.
 18. The process ofclaim 4 wherein nitroglycerin is admixed in the slurry of step (a) in anamount of from about 5 to about 40 percent by weight based on the weightof the densified nitrocellulose particles forming a slurry comprising acontinuous phase of water and a dispersed phase of densifiednitrocellulose particles and nitroglycerin and admixing this slurryuntil substantially all the nitroglycerin, but an equilibriumconcentration of nitroglycerin in water, has been absorbed by thedensified nitrocellulose particles.
 19. The process of claim 19 in whichthe slurry of water, densified nitrocellulose particles andnitroglycerin is heated to a temperature of from about 100* to about140* F. for from about 30 minutes to about 250 minutes to permitcomplete penetration of the nitroglycerin into the densifiednitrocellulose particles.
 20. In a process for the manufacture of asmokeless powder selected from the group consisting ofburning-rate-deterrent-coated, graphite-glazed, andburning-rate-deterrent-coated and graphite-glazed smokeless powders,from at least granulated nitrocellulose, the improvement comprising: a.forming a slurry of at least granulated nitrocellulose particles andwater, b. admixing in the slurry of step (a) at least one memberselected from the group consisting of a burning rate deterrent andfinely divided graphite, to form a resulting slurry comprising acontinuous phase comprising water and a dispersed phase comprisinggranulated nitrocellulose and each member of said group of burning ratedeterrent and finely divided graphite admixed with the slurry of step(a) as described, c. heating the resulting slurry of step (b) at atemperature at which the burning rate deterrent, when present, melts butat at least 150* F. until substantially all of each member of said groupof burning rate deterrent and finely divided graphite dispersed thereinadheres to the granulated nitrocellulose particles, and d. separatingfrom the slurry of step (c), as product of the process, a smokelesspowder selected from said group of burning-rate-deterrent-coated,graphite-glazed, and burning-rate-deterrent-coated and graphite-glazedsmokeless powders.